The Sunwayfoto QRS-01 with D-ring UNC1/4”-20 Screw for Quick Release Plates is a special screw to allow fast and easy mounting and dismounting of most quick release plates.  The D shape can support a max load of 50KG and can be used to attach straps, hand grips, and anything else that will attach to the D shape.  It’s made from 303 stainless steel so it’s tough and has very high corrosion resistance.